Category: Linux Tech

When debugging bash scripts use:
set -o xtrace
to print out each line along with the regular output, as it is executed.

Using Debian with a Intel Corporation Centrino Wireless-N 1000 card… 7. After collecting 30,000 packets (you may leave airodump-ng running): aircrack-ng -1 capturefile.cap 8. The WEP key should then be displayed in the terminal window.9. The collected packet trace may be decrypted with: airdecap-ng -w $wep_key_hex capturefile.cap 10. Exit monitor mode: airmon-ng stop mon0

This is easier and more effective than packet sniffing on a wired network:

Very simple way to test if your WiFi card supports injection: Stop Network Manager: /etc/init.d/network-manager stopPut the card in monitor mode: airmod-ng start wlan0Test using: aireplay-ng -9 mon0 With luck, the following output is displayed:Trying broadcast probe requests…Injection is working!

DNS client configuration can be handled by the standard Router Advertisement Daemon (radvd) – apt-get install radvd Edit /etc/radvd.conf on your Linux Router and insert the following at the end of the file to use Google’s DNS Caching server: RDNS 2001:4860:4860::8888{}; On your Linux clients install rdnssd. To automatically insert the advertised IPv6 DNS servers

IP packet drop can be easily emulated on any section of network using a Linux Bridge and a single iptables command:
iptables -t mangle -A FORWARD -m statistic --mode random --probability 0.01 -j DROP
(where probability is expressed as a value between 0 and 1)

It is often useful to place a Linux system on a specific network cable, to packet sniff or modify the network behaviour. The network setup: [switch] - ethernet cable - [node] becomes: [switch] - ethernet cable - [[Linux Bridge]] - ethernet cable - [node] The only requirement for the Linux Bridge is two physical network

With some bash scripts it can be useful to have them exit as soon as a command fails. To accomplish this have the following just after the “#!/bin/bash” line:
set -o errexit
This will cause the script to…